Despite its most common name, the Norwegian rat is originally from China. The misnomer originated in England in the 1700s. Slightly larger than its very close cousin, the black rat, the Norwegian rat is far more tolerant of cold and therefore has a much greater range. The Norwegian rat is a sewer rat. It also inhabits back alleys, thrives along railroad tracks and in granaries, farms, landfills, junk yards-just about every environment that people inhabit is also inhabited by the Norwegian rat.
The Norwegian rat does not carry bubonic plague, but does harbor several other diseases and parasites, including Weil's disease, ratbite fever, cryptosporidiosis, viral hemorrhagic fever, Q fever, and hantavirus. It serves as a host for Toxoplasma gondi, the parasite that causes toxoplasmosis, and appears to be a carrier for trichinosis.
In an ironic twist of fate, however, the Norwegian rat has probably saved more lives than it has taken. This is the original lab rat. Its use for this purpose came about in the early 1800s after breeders created a line of albino mutants to be used for dog baiting, a practice in which a large number of live rats were put inside a pit with a terrier. Men would place bets on how long it would take the dog to destroy all of the rats. In 1828, in an experiment on fasting, the first of these pure white Norwegian rats was put to use in the lab.
Today the lab rat is used every day in thousands of experiments worldwide. It has helped advance research in almost every possible medical field, from cancer to the study of genetics. Since the 1800s several more subspecies of the Norwegian rat have been created, including a totally hairless variety.
The Norwegian rat is nocturnal. It can be found in the same areas as the black rat. Although these two types of rats inhabit much the same territory, they do not interbreed. The Norwegian rat tends to stick closer to the ground, burrowing and nesting under homes and sheds, whereas the black rat is a skilled climber and inhabits cabbage palms and attics. If any of these rats gains entry into your home or shed, it should be trapped immediately, as it can chew wiring and cause electrical fires, among a host of other problems.
Information on the Norwegian Rat can be found in Sobczak's books "Living Sanibel" and "Living Gulf Coast."
In the Know:
Norwegian Rat (Rattus norvegicus) INVASIVE!
Other names: brown rat, Norway rat, wharf rat, common rat
Status: FL=thriving, IUCN=LC
Length: with tail, 20 in. (50 cm)
Weight: 9-12 oz (250-350 g)
Life span: to 18 months
Reproduces: year round and is a prolific breeder
Found: All Southwest Florida Counties, coastal, near coast, mainland
Months found: JFMAMJJASOND